Development of Novel EBSM System for High-Tech Material Additive Manufacturing Research

Electron beam is more appropriate for metal additive manufacturing (AM) than laser because of its high energy converting efficiency and high absorption for various materials. It becomes a preference for AM study of high-tech material with high melting point, high brittleness or graded material. A novel electron beam selective melting (EBSM) system with dual-material processing capability has been developed in Tsinghua University to meet the wide high-tech material AM research requirement. A vibration driven powder supplier was developed and the supplier had a high compatibility to various powders. A stable supplying rate and a supplying accuracy less than 7.5% were obtained with the supplier. Two powders can be supplied individually to obtain a mixture with tailored proportion for each powder layer. The mixture is homogenous and the actual proportion is close to the desired value. In order to prolong the spreading comb’s lifetime and avoid tooth breaking, a low deformation powder spreading device was designed based on dual inclined combs and a one-way scraping mechanism. The system provides exchangeable building tanks with sizes of 100 ×100 ×100 mm3 and 250 × 250 × 250 mm3, which can save powder when the part is small and the powder is expensive. The novel EBSM system is capable of building parts with single material and has a potential of dual-material processing.Mechanical Engineerin

High frequency variations of Helicobacter pylori isolates in individual hosts in a Chinese population

SummaryBackgroundColonization of individual hosts by multiple Helicobacter pylori genotypes may be one reason why this infection is persistent and difficult to eradicate.MethodsIn order to study the diversity of H. pylori in individuals, a modified randomly amplified polymorphic DNA (RAPD) method was applied using primary culture isolates instead of passaged cultures.ResultsThe results showed that variations in H. pylori were prevalent among individuals in the Chinese population, and the incidence of multiple colonization was 99.1% (115/116), significantly higher than in other reports. Moreover, the number of RAPD genotypes was found to be significantly associated with the process of disease development (p<0.05). Indeed, a trend for a higher number of RAPD genotypes within a single host (up to five genotypes) was observed as the disease developed or became more serious. After subculturing for three generations in our experiment, some genotypes present in the primary cultures were lost. The different genotypes in one patient may have originated from a single ancestral strain, as determined by analysis of six H. pylori housekeeping gene alleles, most of which were shown to be identical.ConclusionsThese results suggest that investigating isolates of the primary culture will better reflect the H. pylori diversity in individuals. Also, they indicate that continuous variation of one strain in the gastric microenvironment may be the main cause of H. pylori diversity in individuals in the Chinese population

Tibetan sheep are better able to cope with low energy intake than Small-tailed Han sheep due to lower maintenance energy requirements and higher nutrient digestibilities

Tibetan sheep are indigenous to the Qinghai-Tibetan Plateau (QTP) and are well-adapted to and even thrive under the harsh alpine conditions. Small-tailed Han sheep were introduced to the plateau because of their high prolificacy and are maintained mainly in feedlots. Because of their different backgrounds, we hypothesised that Tibetan and Small-tailed Han sheep would differ in their utilization of energy intake and predicted that Tibetan sheep would cope better with low energy intake than Small-tailed Han sheep. To test this prediction, we determined nutrient digestibilities, energy requirements for maintenance and blood metabolite and hormone concentrations involved in energy metabolism in these breeds. Sheep of each breed (n = 24 of each, all wethers and 1.5 years of age) were distributed randomly into one of four groups and offered ad libitum diets of different digestible energy (DE) densities: 8.21, 9.33, 10.45 and 11.57 MJ DE/kg Dry matter (DM). Following 42 d of measuring feed intake, a 1-week digestion and metabolism experiment was done. DM intakes did not differ between breeds nor among treatments but, by design, DE intake increased linearly in both breeds as dietary energy level increased (P < 0.001). The average daily gain (ADG) was significantly greater in the Tibetan than Small-tailed Han sheep (P = 0.003) and increased linearly in both breeds (P < 0.001). In addition, from the regression analysis of ADG on DE intake, daily DE maintenance requirements were lower for Tibetan than for Small-tailed Han sheep (0.41 vs 0.50 MJ/BW0.75, P < 0.05). The DE and metabolizable energy (ME) digestibilities were higher in the Tibetan than Small-tailed Han sheep (P < 0.001) and increased linearly as the energy level increased in the diet (P < 0.001). At the lowest energy treatment, Tibetan sheep when compared with Small-tailed Han sheep, had: 1) higher serum glucose and glucagon, but lower insulin concentrations (P < 0.05), which indicated a higher capacity for gluconeogenesis and ability to regulate glucose metabolism; and 2) higher non-esterified fatty acids (NEFA) and lower very low density lipoprotein (VLDL) and triglyceride (TG) concentrations (P < 0.05), which indicated a higher capacity for NEFA oxidation but lower ability for triglyceride (TG) synthesis. We concluded that our prediction was supported as these differences between breeds conferred an advantage for Tibetan over Small-tailed Han sheep to cope better with low energy diets

Phase transitions in self-dual generalizations of the Baxter-Wu model

We study two types of generalized Baxter-Wu models, by means of transfer-matrix and Monte Carlo techniques. The first generalization allows for different couplings in the up- and down triangles, and the second generalization is to a $q$-state spin model with three-spin interactions. Both generalizations lead to self-dual models, so that the probable locations of the phase transitions follow. Our numerical analysis confirms that phase transitions occur at the self-dual points. For both generalizations of the Baxter-Wu model, the phase transitions appear to be discontinuous.Comment: 29 pages, 13 figure

Silhouette-based 3D model for zebrafish high-throughput imaging

Computer Systems, Imagery and Medi

Three-dimensional reconstruction and measurements of zebrafish larvae from high-throughput axial-view in vivo imaging

Animal science

First Report of Alternaria Black Spot Disease Caused by Alternaria alternata on the Invasive Weed Solanum rostratum in Xinjiang, China

Solanum rostratum is a noxious weed, native to Mexico and the USA, which has invaded Liaoning, Jilin, Hebei, Inner Mongolia, Shanxi, Xinjiang and Beijing, China (Eminniya et al., 2013). In August 2015, foliar symptoms of yellowish to black spots were observed on plants of S. rostratum nearby an agricultural plantation in Changji, Xinjiang. The following year, about 17% of the 206 plants surveyed on about 0.2 ha of deserted farmland were infected from July-September (at 19-35°C under 29-97% RH)

Possible Role of Protein CPG15 in Hippocampal Mossy Fiber Sprouting Under Conditions of Pentylenetetrazole Kindling

We examined changes in expression of the candidate plasticity-related gene 15 (CPG15) in the dentate gyrus (DG) and hippocampal CA3 region in the pentylenetetrazole (PTZ) kindling model and investigated the role of this gene in the phenomenon of mossy fiber sprouting (MFS). Experimental rats were divided into the control and PTZ groups. The epileptic model was created by intraperitoneal PTZ injection, while control rats were injected with saline. At days 3, 7, 14, 28, and 42 after the first PTZ injection, Timm staining was scored in the CA3 hippocampal area, and a product of CPG15 (protein CPG15) was labeled in the DG stratum granulosum and in the CA3 area using immunohistochemistry. The Timm scores in the CA3 region increased gradually from day 3 and were significantly higher than those in the control within the subsequent period. The level of CPG15 protein in the DG and CA3 area decreased gradually until day 14 and returned to the normal level at day 28. The results obtained indicate, for the first time, that CPG15 may be involved in the process of MFS. Understanding the molecular mechanisms underlying this phenomenon may lead to successful therapeutic interventions that limit epileptogenesis.Ми досліджували зміни експресії продукту гена CPG15 у зубчастій звивині (ЗЗ) та зоні CA3 гіпокампа в моделі пентилентетразолового (ПТЗ-) кіндлінгу та можливу роль цього гена у феномені спрутингу моховитих волокон (СМВ). Піддослідні щури були поділені на групи контролю та ПТЗ-кіндлінгу. Модель епілепсії створювали за допомогою внутрішньоочеревинних ін’єкцій пентилентетразолу (ПТЗ); контрольним щурам ін’єкували фізіологічний розчин. На третю, сьому, 14-ту, 28-му та 42-гу добу після першої ін’єкції ПТЗ оцінювали забарвлення, за Тіммом, у зоні CA3. Локалізацію протеїну CPG15 у stratum granulosum ЗЗ та зоні CA3 гіпокампа визначали з використанням імуногістохімічної методики. Інтенсивність забарвлення, за Тіммом, у зоні CA3 поступово збільшувалася починаючи з третьої доби та була вірогідно вищою, ніж така в контролі, протягом усього наступного періоду. Рівень протеїну CPG15 у ЗЗ та полі CA3 поступово зменшувався до 14-ї доби та повертався до нормальних значень на 28-му добу. Отримані результати вперше вказують на те, що CPG15 може бути залученим у процес СМВ. Зрозуміння молекулярних механізмів, на яких базується цей феномен, може призвести до розробки успішних терапевтичних заходів, котрі обмежували б епілептогенез

Parametrization of Born-Infeld Type Phantom Dark Energy Model

Applying the parametrization of dark energy density, we can construct directly independent-model potentials. In Born-Infeld type phantom dark energy model, we consider four special parametrization equation of state parameter. The evolutive behavior of dark energy density with respect to red-shift $z$, potentials with respect to $\phi$ and $z$ are shown mathematically. Moreover, we investigate the effect of parameter $\eta$ upon the evolution of the constructed potential with respect to $z$. These results show that the evolutive behavior of constructed Born-Infeld type dark energy model is quite different from those of the other models.Comment: 5 pages, 4 figures, Accepted for publication in Astrophysics & Space Scienc